The present application relates to a display device including a thin film transistor (TFT) and a wiring layer, a method of manufacturing the display device, and an electronic unit.
In recent years, a perfectly transparent (light transmissive) display is desired, and a transparent conductive oxide film of ITO (indium-tin-oxide) or the like is used as an electrode of a transistor. Since oxide semiconductors containing zinc (Zn), indium (In), gallium (Ga), or the like offer favorable contact with transparent conductive oxide films, a TFT in which such oxide semiconductors are used as a semiconductor layer is under development (for example, Japanese Unexamined Patent Application Publication No. 2010-98280).
Compared to TFTs using amorphous silicon (a-Si:H), a TFT using an oxide semiconductor offers higher electron mobility, and has excellent electric characteristics. In addition, a TFT using an oxide semiconductor is expected to offer high mobility even in the case where it is formed under a cold condition at around room temperature, and therefore, such a TFT using an oxide semiconductor is actively developed in the field of electronic devices such as a light-emitting device and a transparent conductive layer, other than a TFT (for example, Japanese Unexamined Patent Application Publication (Published Japanese Translation of PCT Application) No. 2007-519256; Japanese Unexamined Patent Application Publication No. 2008-85048; Cetin Kilic, et al., “n-type doping of oxides by hydrogen”, Applied Physics Letters, Jul. 1, 2002, vol. 81, No 1, pp 73-75; and Japan Society for the Promotion of Science, The 166th Committee on Photonic and Electronic Oxide ed., “Technology of Transparent Conductive Layer” pp 150-152).
As a TFT using an oxide semiconductor, a bottom-gate type TFT and a top-gate type TFT have been reported. The structure of the bottom-gate type is similar to that of a bottom-gate type amorphous silicon TFT which is currently used in liquid crystal displays, and therefore the manufacturing process of the amorphous silicon TFT is applicable. TFTs of the bottom-gate type include on a substrate thereof a gate electrode, a gate insulating film, a semiconductor thin film, and a source/drain electrode in this order, and one of the source/drain electrode is connected to a wiring layer such as a scan line and a signal line. Since the resistance of a transparent conductive oxide film is high, it is difficult to use the transparent conductive oxide film as a main wiring layer. Consequently, a low-resistance metal such as aluminum (Al) is used as the above-mentioned wiring layer.